Expansion joints for rigid metallic pipes

ABSTRACT

The disclosure relates to an expansion joint for metallic pipes, the joint comprising a reinforced rubber body in the form of an annular loop having enlarged lateral edge portions and a pair of locking members for connecting the edge portions of the body to adjacent portions of the pipe ends. Each ring is provided with an undercut groove to receive a portion of the enlarged lateral edge portion. Each locking ring comprises a pair of annular elements disposed in facing contact and interlocked. The first annular element has a greater thickness and is directed towards the outer side of the rubber body. The second element extends outwardly beyond the innermost edge of the first element to thus form the undercut groove.

United States Patent F ischetti 1 May 30, 1972 [54] EXPANSION JOINTS FORRIGID METALLIC PIPES [72] Inventor: Pasquale F lschetti, Saronno, Italy[73] Assignee: Pirelll, S.p.A., Milan, Italy [22] Filed: Mar. 11, 1970[21] Appl. No.: 18,610

1,253,532 11/1967 Germany ...285/229 Primary E.xaminer-Dave W. ArolaAttorney-Stevens, Davis, Miller & Mosher [57] ABSTRACT The disclosurerelates to an expansion joint for metallic pipes, the joint comprising areinforced rubber body in the form of an annular loop having enlargedlateral edge portions and a pair of locking members for connecting theedge portions of the body to adjacent portions of the pipe ends. Eachring is provided with an undercut groove to receive a portion of theenlarged lateral edge portion. Each locking ring comprises a pair ofannular elements disposed in facing contact and interlocked. The firstannular element has a greater thickness and is directed towards theouter side of the rubber body. The second element extends outwardlybeyond the innermost edge of the first element to thus form the undercutgroove.

10 Claims, 5 Drawing Figures PATENTEDMAY 30 972 SHEET 10F 2.

INVENTOR PASQUALE FISCHETT/ BY 819mm, @rwis /Lflu $064 ATTORNEYSPATENTEDHAY 30 I972 sum 2 or 2 FIG.5

EXPANSION JOINTS FOR RIGID METALLIC PIPES The present invention relatesto flexible expansion joints for metallic pipes which comprise areinforced rubber body in the form of at least one annular loop withlateral portions extending outwardly and the edge portions each havingan enlarged head, a pair of locking rings are provided for connectingthe edge portions to adjacent portions of the pipe.

As is well known, expansion joints for rigid pipes are pipe elementsadapted to compensate, by means of their deformation or by the mutualdisplacement of their component parts, the length variations of the pipeto which they are applied. Such length variations can for instance bedue to variations in the temperature of the conveyed fluid, and/or inthe room temperature, or to the settlement of the pipe supports.

In presently known expansion joints, the locking ring on each side ofthe joint is provided, on its inner edge, with an undercut circulargroove, intended to receive the corresponding edge of the rubber body.Up to now, the locking rings of this type were made in a single piece.The presence of the groove in the locking ring influenced the ringthickness and involved a particular processing of this piece. Regardlessof the features of the locking ring, when the rubber body was providedwith lateral tubular extensions, even of cylindrical shape, between theannular loop and the edges, it required a reinforcing structure whichhad to be the more resistant the greater the diameter of the extensions,in order to limit the deformation of the joint within stated limits andto allow higher service pressures. In fact, at an equal pressure of theconveyed fluid, the higher the stress exerted the greater the diameter.

An expansion joint having a rubber body provided with a reinforcingstructure limited to the presence of layers of textile material disposedfrom one side of the body to the other; that is, devoid of auxiliaryreinforcements inserted at the lateral extensions, had the disadvantageof an immediate massive deformation due to its expansion. Thisdeformation could cause interferences with the bolts fastening thelocking rings or with other elements, which could give rise to tears,and in any event caused a prejudicial increase in the stresses on therubber body, due to the increase of diameter consequent to theexpansion. Therefore, expansion joints of this kind gave a satisfactoryresult only if they had a reduced diameter and if they were subjected toa reduced service pressure. However, for relatively large diameters ofthe rubber body of the expansion joint, the structure had to becompleted with the insertion of strong reinforcements, as for instancemetal rings or wire coils, which had to remain embedded in the side ofthe lateral extensions. In this case, however, the rubber body, inparticular in its lateral extensions, had an irregular thickness.

Moreover, in the above described prior art expansion joints, the strongreinforcements and the considerable wall thickness of the rubber body,on the other hand, imparted to the expansion joint a certain rigiditywhich limited the performance of the joint itself, in particular inrespect of its behavior under vibrations of high frequency and lowamplitude. In fact, an expansion joint having a certain rigidity wasunable to give a satsifactory performance when it was inserted betweenpipes subjected to vibrations of high frequency and low amplitude. Asthe joint, to absorb vibrations of such a kind, had to be very flexible,only the joints having a rubber body of relatively small diameter wereable to give satisfactory results in this specific respect.

The present invention aims at eliminating the above describeddisadvantages as regards in particular the locking rings and, in a moregeneral sense, as regards the behavior of the joint under vibrations ofhigh frequency and low amplitude.

An object of the invention is a flexible expansion joint of any kind,provided with two locking rings of simple construction.

A further object of the invention is a flexible expansion joint whichmay give a satisfactory performance even if it is provided with lateraltubular extensions of relatively large diameter.

The Applicant has found that, if the locking ring has a compositestructure, the problem of its simple construction can be solved, and itis also possible to create the premises for the solution of the problemconcerning a broadening of the joint employment.

Briefly summarized, an essential feature of the present inventionresides in the fact that each metallic locking ring, as described abovefor presently known flexible expansion joints, embodies a pair ofannular elements disposed in facing contact and interlocked, the firstelement having a greater thickness and being directed towards the outerside of the rubber body, and the second element, preferably made ofstamped plate, extending beyond the inner edge of the first element andbeing directed outwardly to form with the first element an undercutgroove.

According to another embodiment of the invention, in the above describedlocking ring which can be applied on a rubber body provided withtubular, even cylindrical elements at the sides of at least an annularloop, the second annular element, as a succession to the groove, is benttowards the loop to form a cylindrical prolongation of such length andinner diameter that it entirely covers and is in contact with thecorresponding lateral extension of the rubber body even when the jointis not in service.

The expression entirely covers and is in contact with," in reference tothe cylindrical prolongation of the locking ring used in thespecification and in the appended claims, means that the prolongationcovers the corresponding lateral tubular extension of the rubber bodyalong the entire length of the latter and that, even when the joint isnot in service, the two mutual extensions are in total or partialcontact, it being understood that, in case of partial contact, theremaining part of the concerned rubber extension is such as to beimmediately put into contact with the respective prolongation of thelocking ring, as soon as the joint is put into service.

The present invention will be more clearly understood from the followingdescription, made by way joint non-limiting example with reference tothe attached drawings, in which:

FIG. 1 is a lateral view, partially in section, of an expansion jointaccording to the invention;

FIG. 2 is a lateral view, partially in section, of an expansion jointaccording to the invention, in which the rubber body is provided withcylindrical lateral extensions;

FIG. 3 is a lateral view, partially in section, of an alternativeembodiment of the joint of FIG. 2.

FIG. 4 is a lateral, partially sectioned view of an alternativeembodiment of the joint of FIG. 3; and

FIG. 5 is a lateral partially sectioned view of the joint of FIG. 3showing the inclusion therein of a further element.

The expansion joint shown in FIG. 1 comprises a rubber body 1,substantially formed by an annular loop 2 protruding outwardly, and bytwo metallic locking rings 3. These rings are intended to receive theoutwardly projecting edges, having enlarged beads, of the rubber body,as it will be explained herebelow and also to be fastened by means ofbolts to the flanges of adjacent portions of the pipe, in order toprovide a secure connection of the joint to the pipe itself.

Layers of fabric 4, which extend from one end 5 to the other end 6,passing therefore through the entire section of loop 2, constitute thereinforcing structure of the rubber body. Each locking ring 3 is formedby two annular elements 7 and 8, which face each other in frictionalcontact and are interlocked to form a single unit.

Annular element 7 has a thickness greater than that of the annularelement 8, which is preferably made of stamped plate and is directedtowards the outer side of the rubber body, which is intended to comeinto contact with the flange of the length of rigid pipe to be connected(not shown).

The annular element 8, which is consequently turned towards the loop 2,protrudes with its portion 9 beyond the inner edge 10 of the ring 7, andis bent towards the joint ends to form with said edge 10 an undercutgroove 11. Moreover, the outermost portion 12 of the annular element 8is folded against the conical outer edge 13 of the ring 7, so that thetwo elements 7 and 8 are interlocked.

The corresponding edges 14 of the rubber body 1 are encased withingrooves 11 of the locking rings. As each edge 14 protrudes in the outerradial direction and has in section an enlarged bead, it remains housedwithin the groove 11 when the locking ring 3 is finnly connected to thecorresponding flange (not illustrated) of the pipe by means of boltspassing through holes, one of which is indicated with 16, and thecorresponding hole (not illustrated) of said flange. The bolts, ofcourse, cooperate to the secure connection of annular elements 7 and 8when the expansion joint is assembled on the pipe. Each of the edges 14of the rubber body 1 has at 17 a toothed profile, which is provided inorder to provide a tight fit when it is in contact with thecorresponding flange of the metallic pipe (not illustrated).

Moreover, each edge 14 is reinforced by means of an annular core made ofmetal or of any other suitable material, which is embedded in therubber. The ends of the textile layer 4 are wound up about said cores15.

Further, locking rings 3 can be combined with rubber bodies of adifferent type. For example, FIG. 2 illustrates an expansion joint, inwhich the rubber body 1 has a loop 2 and two cylindrical lateralextensions 2 and 2". In the locking rings 3 of this joint, havingannular elements 7 and 8, the element 8 is folded, in succession to thegroove 11, towards the loop 2 to form a prolongation 18, having such alength and inner diameter that it covers and is in contact with theentire outer surface of the corresponding cylindrical lateral extensions2' and 2" of said rubber body, even when the joint is not in use.

It is preferable that the free edge 19 of the cylindrical prolongation18 of the annular element 8 of the locking ring 3 be curved upward andbackward. In this way, the loop 2 is prevented from being cut when itcomes in contact with the metallic edges under deformation due tosqueezing or angular displacement.

The advantages afforded by this form of locking ring are evident. As oneof the two components of each locking ring 3; that is the annularelement 8, is formed of a plate, such element can be drawn to attain itsintricate pre-established structure.

Moreover, the annular element 8 can be interlocked with the annularelement 7 by simply rolling the portion 12 of the former against theconical edge 13 of the latter. The annular element 8, however, can besecured to the annular element 7 in a different way, as for instance byspot welding. The union of the annular elements 7 and 8 forms the groove11 of the locking ring 3.

The same system is followed when it is desired to obtain a locking ringin which the annular element 8 is provided with the cylindricalprolongation 18.

In the expansion joint according to the invention, which is providedwith locking rings having a composite structure and with cylindricallateral prolongations, the prolongations, which are metallic, constitutean efficient reinforcement to the underlying tubular extensions of theloop of the rubber body. It follows that the reinforcing structureembedded in the wall of the rubber body can be for instance limited to aplurality of layers of fabric of any kind, made of textile fibers, metalwires or other material, disposed from one end to the other, even if therubber body has a relatively large diameter at its lateral cylindricalextensions.

In fact, the reinforcement of the rubber body in the event of strongstresses, which would tend to deformate it during expansion, remainscommitted to the metallic cylindrical prolongations 18 of the lockingrings. In this way, even if it has a large diameter, the expansion jointcan be constituted by a rubber body having a relatively small andconstant wall thickness, from one of its ends to the other.Consequently, even if it has a large diameter, the rubber body of thejoint according to the invention has a continuous surface from one endto the other, different from the rubber bodies obtained up to this time,which, in case of large diameters, were to be provided with strongreinforcements at their lateral cylindrical extensions and thereforegiving rise to differences of wall thickness between the extensions andthe loop.

In rubber bodies heretofore produced, considerable thickness of therubber portion presented a serious limitation in the mutual deformationof the two joint arms, this does not take place in the joint accordingto the present invention, since this body has a relatively smallthickness, which is constant from one end to the other, even with theloop is of a large diameter and greater size.

For all the above indicated reasons, the joint according to theinvention has relevant flexibility characteristics, which allow it toabsorb high frequency and low amplitude variations, even through thediameter of the rubber body is relatively large.

In a further embodiment of the invention, illustrated by FIG. 3, thefree curved edge 19 of a cylindrical lateral prolongation of a lockingring 3 and the corresponding edge 19 of the cylindrical lateralprlongation of the other locking ring 3, of an expansion joint areconnected to an intermediate connecting element 20, which passes overthe loop of the rubber body to act as limit means for the jointexpansion.

More precisely, the intermediate connection element 20 is constituted bytwo terminal rings 21, secured on the mutual bent edges 19 of theprolongations of the locking ring 3 and by interlaced wires or cords 22,made of metal or of other suitable material, which pass from oneterminal ring to the other through holes 23. The terminal rings 21 canbe connected in a difierent way, for instance by means of a wire net 24in FIG. 4.

This limiter for the expansion joint affords considerable advantagesover the conventional linear limiters already known, which gavesatisfactory results in the event of an elongation of the expansionjoint, but permitted angular deformations between the arms of the jointitself, which were too small for the requisites of its service.

This limitator allows, in fact, considerable angular deformationsbetween the two joint arms. The presence of the limitator, placed intocontact with the loop of the expansion joint, can be used to insert andto maintain in place a protective material 25 (FIG. 5) which may coverand protect the loop. This material can have a protective action againstfire and may be therefore made of asbestos or of aluminized fabrics, oragainst possible accidental damages due to shocks or impacts againstsharp bodies. If desired, the whole unit formed by the prolongations ofthe locking rings and by the intermediate connecting ring can retain amaterial protecting the entire outer surface of the flexible jointhaving lateral cylindrical extensions.

What is claimed as new is:

l. A flexible expansion joint for inter-connecting two pipes,comprising: an annular shaped body of reinforced rubber having oppositeaxial ends and a central portion which in axial cross-section protrudesradially convexly from said ends, said ends each including an annularradially outwardly projecting collar portion, a pair of metallic lockingrings, for each of said ends, each pair of rings defining an annulargroove open at the outer axial end thereof, each of said collar portionsbeing lockingly engaged in a respect one of said grooves, the rings ofeach of said pair being axially adjacent and secured to each other andin facing contact with each other, aid groove being formed betweenrespective radially spaced apart walls of said I'H'lgS.

2. The joint of claim 1, a first of said rings having a conical radiallyouter wall, the second of said rings having an outer edge portion bentover said conical wall whereby said rings are lockingly engaged againstaxial movement relative to each other.

3. The joint of claim 2, wherein said body includes tubular portions ofconstant diameter extending from said central portion to said ends, eachof said second rings comprising an extent which is bent axiallyoutwardly to define a wall of said groove and is then bent axiallyinwardly to define a cylinder circumscribing the entire outer surface ofsaid tubular portrons.

4. The joint of claim 3, the axially innermost end of said cylinderbeing bent'axially outwardly to face away from said central convexportion of said body.

5. A joint as in claim 3, characterized in that the rubber body isprovided, as a reinforcing structure, with layers of fabric reinforcingfibers, which extend from one end of the body to the other.

6. A joint as in claim 3, characterized in that the bent innermost endof the cylindrical prolongation of the second element of a locking ring,and the corresponding edge of the second element of the other lockingring are connected to an intermediate connection element, which passesover the loop of the rubber body to act as a limiter.

7. A joint as in claim 6, characterized in that said angular connectionelement is provided with terminal rings and a lacing element, whichpasses through holes formed in said terminal rings which, on their turn,have in cross section a shape complementary to that of the correspondingbent free edge of the cylindrical prolongation of the second element ofthe locking ring on which each tenninal ring is secured.

8. A joint as in claim 7, characterized in that a net, made of wire orof a like material, is used in place of said lacing element.

9. A joint as in claim 6, characterized in that a protective material,is interposed between the annular intermediate connecting element andthe loop of the rubber body.

10. A joint as in claim 9, characterized in that said protectivematerial extends below the cylindrical lateral prolongations of thelocking rings.

* l III

1. A flexible expansion joint for inter-connecting two pipes,comprising: an annular shaped body of reinforced rubber having oppositeaxial ends and a central portion which in axial crosssection protrudesradially convexly from said ends, said ends each including an annularradially outwardly projecting collar portion, a pair of metallic lockingrings, for each of said ends, each pair of rings defining an annulargroove open at the outer axial end thereof, each of said collar portionsbeing lockingly engaged in a respect one of said grooves, the rings ofeach of said pair being axially adjacent and secured to each other andin facing contact with each other, aid groove being formed betweenrespective radially spaced apart walls of said rings.
 2. The joint ofclaim 1, a first of said rings having a conical radially outer wall, thesecond of said rings having an outer edge portion bent over said conicalwall whereby said rings are lockingly engaged against axial movementrelative to each other.
 3. The joint of claim 2, wherein said bodyincludes tubular portions of constant diameter extending from saidcentral portion to said ends, each of said second rings comprising anextent which is bent axially outwardly to define a wall of said grooveand is then bent axially inwardly to define a cylinder circumscribingthe entire outer surface of said tubular portions.
 4. The joint of claim3, the axially innermost end of said cylinder being bent axiallyoutwardly to face away from said central convex portion of said body. 5.A joint as in claim 3, characterized in that the rubber body isprovided, as a reinforcing structure, with layers of fabric reinforcingfibers, which extend from one end of the body to the other.
 6. A jointas in claim 3, characterized in that the bent innermost end of thecylindrical prolongation of the second element of a locking ring, andthe corresponding edge of the second element of the other locking ringare connected to an intermediate connection element, which passes overthe loop of the rubber body to act as a limiter.
 7. A joint as in claim6, characterized in that said angular connection element is providedwith terminal rings and a lacing element, which passes through holesformed in said terminal rings which, on their turn, have in crosssection a shape complementary to that of the corresponding bent freeedge of the cylindrical prolongation of the second element of thelocking ring on which each terminal ring is secured.
 8. A joint as inclaim 7, characterized in that a net, made of wire or of a likematerial, is used in place of said lacing element.
 9. A joint as inclaim 6, characterized in that a protective material, is interposedbetween the annular intermediate connecting element and the loop of therubber body.
 10. A joint as in claim 9, characterized in that saidprotective material extends below the cylindrical lateral prolongationsof the locking rings.